The present invention relates to a transmission control device including a multi-speed transmission and control means. The transmission changes the speed of rotations caused by driving force from a driving source of a vehicle, and outputs the rotations to driving wheels. The control means controls the speed change by the transmission.
As recited in Japanese Unexamined Patent Application Publication No. 2008-24100 (patent document 1), for example, a twin-clutch automatic transmission (multi-speed transmission) has been conventionally known as a transmission for a vehicle. The twin-clutch automatic transmission includes two input shafts and two clutches. The two clutches switch inputs of driving force to the two respective input shafts. Such a twin-clutch automatic transmission generally performs selection of a gear in advance (pre-shift) other than a gear to which the clutch is connected and transmits motive power. In this pre-shift, based on, for example, a vehicle speed, an accelerator operation amount, and a deceleration rate, a target pre-shift position is selected to be one position higher (in acceleration) or one position lower (in deceleration) than a traveling gear to which the clutch is connected.
Normally, at the time of deceleration of the vehicle, the target pre-shift position is generally selected to be one position lower than the traveling gear. However, when the deceleration rate of the vehicle is high, the pre-shift does not follow the shift position change to the target shift position. This causes a problem of degradation in responsiveness of the driving force at the time of re-acceleration of the vehicle.
In this regard, in the transmission system recited in patent document 1, two start clutches are both connected, and four dog clutches are made neutral at the time of sudden deceleration of the vehicle. This improves responsiveness at the time of re-acceleration of the vehicle. That is, the transmission system recited in patent document 1 includes a plurality of shift actuators, which enable the four dog clutches to be neutral simultaneously. Therefore, the above-described gear change control improves responsiveness at the time of re-acceleration of the vehicle.
However, for example, Japanese Translation of PCT International Application Publication No. JP-T-2004-518918. (patent document 2) discloses a twin-clutch transmission including only one gear actuator. In the case of this twin-clutch transmission, in order to make all the gears neutral, it is necessary to perform a plurality of operations including a selection operation and a shift operation by the gear actuator. Since a resistance against the selection operation is relatively small, the selection operation is a relatively quick operation. However, the shift operation is affected by a resistance against an in-gear operation (engagement operation between a gear and a rotation shaft), and consequently, the shift operation is a relatively slow operation. In the shift operation, therefore, in response to a request of re-acceleration of the vehicle when a driver steps on an accelerator pedal, for example, responsiveness of the re-acceleration is disadvantageously degraded.